The invention relates to a device for the processing of compressed air for a commercial vehicle, with an inlet connection for connecting a compressor, a ventilation (also referred to as a vent), a compressor control outlet for acting with pressure upon a control inlet of the compressor, an air dryer unit, a pneumatically activatable shut-off valve which follows the inlet connection in the flow direction and which can be transferred from an open to a closed state by the action of pressure, a pneumatically activatable pressure regulating valve which is arranged between an outlet connection of the shut-off valve and the ventilation and which can be transferred from a closed to an open state by the action of pressure, a compressor control device which has a first solenoid valve and via which, in an excited state of the first solenoid valve, compressed air can be supplied to a control inlet of the shut-off valve and to the compressor control outlet, and a second solenoid valve which, in the excited state, allows a backflow of compressed air through the air dryer unit and the pressure regulating valve to the ventilation and via which, in the excited state, a control inlet of the pressure regulating valve can be acted upon with compressed air.
The invention relates, furthermore, to various methods for operating such a device for the processing of compressed air.
Devices for the processing of compressed air contain as central components a pressure regulator, an air dryer unit and a multiple-circuit protection valve. In the electronic design of the device for the processing of compressed air, an electronic control is integrated as a further essential component into the device. Compressed air is supplied by a compressor to the device for the processing of compressed air, this compressed air supply being delivered via the air dryer unit and the multiple-circuit protection valve to various consumers of a commercial vehicle, for example to the brake system of the traction vehicle and trailer, to a lift-axle device and to other secondary consumers, as they are known. The multiple-circuit protection valve in this case serves particularly the purposes of controlling the filling sequence of the various consumer circuits and of protecting the various circuits with respect to one another or of topping them up in a suitable way. The pressure regulator is provided in order, when the maximum permissible system pressure is overshot, that is to say in the case of additional compressed air not required, to discharge the surplus compressed air via ventilation. The air dryer unit is provided in order to supply dried and purified air to the consumers and thereby to avoid premature wear of the consumers due to corrosion and comparable processes.
Since the air dryer unit is laden with moisture and other foreign particles during the operation of the device for the processing of compressed air, it is necessary to regenerate the latter from time to time, either at regular time intervals or when specific preconditions are present, for example a signal from a moisture sensor. The regeneration of the air processing plant then takes place in that air is extracted from the reservoirs previously filled with dry compressed air and flows through the air dryer unit in a direction which is opposite to the flow direction when the system is being filled. Since a flow in such a direction is undesirable outside the regeneration phases, this is prevented by a nonreturn valve which follows the air dryer unit. During the regeneration phases, this nonreturn valve is bypassed by the changeover of a solenoid valve.
There are various concepts for operating the compressor during the regeneration phases. For example, it is possible to allow the compressor to continue to convey during idling, that is to say to discharge via a ventilation line the air which is delivered by the compressor. Other concepts provide for switching off the compressor during the regeneration phase in order to save energy. To make this possible, the device for the processing of compressed air has provided on it a compressor control outlet, to which a control inlet of the compressor is connected. It is thereby possible to supply compressed air in a directed manner to the control inlet of the compressor in order to switch off the latter.
WO 02/24506 A1 describes such a concept, in which a switching off of the compressor takes place, with reference to several embodiments. According to one of these embodiments, there is provision, in addition to switching off the compressor, for closing a shut-off valve in the conveying line of the compressor, in order thereby to avoid an unnecessary pressure loss in the conveying line. When the compressor is restarted, a smaller volume consequently has to be brought anew to the desired pressure. However, according to this exemplary embodiment of WO 02/24506 A1, only a pressure breakdown downstream of the shut-off valve is prevented.
The object on which the invention is based is to make available a device for the processing of compressed air, having improved properties, while, in particular, an unnecessary pressure loss in the compressor line is to be avoided.
This object is achieved by means of the features of the independent claims. Advantageous embodiments of the invention are specified in the dependent claims.
The invention builds on the generic device for the processing of compressed air, in that, with the first solenoid valve excited, the pressure in a line between the compressor and the shut-off valve is essentially maintained. Consequently, when compressor operation resumes, the volume which is held under pressure does not have to be filled anew, thus giving rise to a saving of energy and of time.
This functionality may be implemented particularly in that the first solenoid valve, besides activating the shut-off valve and the control valve, does not assume any further control functions relating to the line between the compressor and the shut-off valve. Hence, besides acting with the pressure upon the compressor control inlet, the first solenoid valve merely activates the shut-off valve, and, in particular, there is no activation of a further valve, via which compressed air could escape from the compressor line. The pressure in the line region upstream of the shut-off valve is therefore maintained when the compressor is switched off.
It is preferable that the compressor control device has a control valve, that compressed air delivered by the first solenoid valve can be supplied to the compressor control outlet via the control valve, and that, in the absence of compressed air delivered by the first solenoid valve, the control valve connects the compressor control outlet to the ventilation. Since the compressor control device has a solenoid valve and a control valve, the aerating and exhausting ventilation of the control inlets involved can take place reliably and in a controlled way. In particular, although compressed air is supplied to the control inlet of the compressor by the control valve and is delivered directly by the solenoid valve, there is nevertheless no need for ventilation of the control inlet to take place via the solenoid valve, since the control valve can make available a direct connection of the compressor control outlet to the ventilation.
Furthermore, there may be provision for the shut-off valve to be able to be transferred into its open state by means of a spring force. The shut-off valve is therefore always opened, independently of the conveying pressure of the compressor, when the control inlet of the shut-off valve is not acted upon with compressed air. By such action of pressure upon the control inlet, the shut-off valve can then be closed counter to the spring force.
It is particularly expedient that a safety valve is provided which limits the pressure in the line between the compressor and the shut-off valve. Since the compressor conveying line is not ventilated upstream of the shut-off valve in the conveying intermission, it is expedient to provide a safety valve, in order thereby to prevent a pressure rise in said line branch. Such a safety valve may be provided inside the device for the processing of compressed air or else be implemented as an external component. As a particular embodiment, a shut-off valve with an integrated safety valve offers complete functionality in terms of maintaining the pressure and affords the required safety, while at the same time having a low outlay in terms of assembly and a small construction space requirement.
The invention relates, furthermore, to a method for operating a device for the processing of compressed air according to the invention, having the steps:
transfer of the first solenoid valve into an excited state,
transfer of the second solenoid valve into an excited state,
maintaining these states for the purpose of the regeneration of the air dryer unit, a pressure in a line between the compressor and the shut-off valve being essentially maintained,
transfer of the second solenoid valve into a non-excited state, and
transfer of the first solenoid valve into a non-excited state.
According to this method, the regeneration of the air dryer unit in the device for the processing of compressed air is implemented, while at the same time the pressure in the compressor conveying line is maintained.
Furthermore, however, the invention also makes available a method for operating a device for the processing of compressed air according to the invention, having the following steps:
transfer of the second solenoid valve into an excited state, and
maintaining a non-excited state of the first solenoid valve and the excited state of the second solenoid valve for the purpose of regenerating a line between the compressor and the device for the processing of compressed air.
Thus, moisture and dirt can be removed, as required, from the compressor conveying line, since, in the described switching states of the solenoid valves, the compressor continues to convey in the direction of ventilation.
The method may expediently be developed in that it is carried out at regular time intervals.
Alternatively or additionally, however, there may also be provision for the method to be carried out in the presence of one or more conditions. Such events may be given, for example, by the detection of specific measurement values of sensors, for example pressure and/or temperature sensors.
The invention, then, is explained by way of example by means of particularly preferred embodiments, with reference to the accompanying drawings in which:
In the following description of the drawings, the same reference symbols designate identical or comparable components.